Overtone headstock



FIG. 1 is a perspective view of an overtone headstock showing my new design, the details shown in broken lines form no part of the claimed design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a right side view thereof; and,

FIG. 7 is a left side view. 

I claim the ornamental design for an overtone headstock, as shown and described. 